1. Field of the Invention
The present invention relates to a three-dimensional measuring system for measuring a three-dimensional shape of a measurement object in a noncontact manner.
2. Description of the Prior Art
Conventionally, noncontact three-dimensional measurement (three-dimensional measurement) is often used for measuring a three-dimensional shape of a measurement object. The three-dimensional measurement includes a passive type such as a lens focus method or a stereo image method and an active type such as a light radar method or a light projection method. In the stereo image method, the measurement object is shot from plural different positions by a camera, for example. Then, three-dimensional coordinates of each point on the measurement object are calculated from the plural obtained images by the principle of triangulation. In addition, according to the light projection method, detection light is projected to the measurement object, and light reflected by the measurement object is received by an imaging element. If slit light is used as the detection light, the method is called a slit light projection method (it is also called an optical cutting method). According to the slit light projection method, the slit light is deflected so that the measurement object is scanned optically, and three-dimensional coordinates of each point on the measurement object is calculated from deformation degree of the slit light based on a surface shape of the measurement object by the principle of triangulation.
In order to obtain a complete set of three-dimensional shape data of one measurement object, it is necessary to perform the three-dimensional measurement of the measurement object plural times so as to combine and integrate the plural obtained three-dimensional shape data.
Conventionally, it is common method to measure a measurement object using a three-dimensional measuring device by manual operation of an operator. It is also common to refer to design information or CAD information of the measurement object in order to assist the three-dimensional measurement or other various measurements (see Japanese unexamined patent publication No. 2002-328952).
In addition, a device for measuring a surface shape and dimensions accurately is proposed, in which plural pieces of three-dimensional position information of a noncontact displacement gage is determined on a measurement path corresponding to plural measurement points set on the measurement object (see Japanese patent No. 7-18698).
However, there is a case where a part of a measurement object cannot be measured by the three-dimensional measuring device depending on a surface shape of the measurement object. In other words, a real three-dimensional measuring device has its predetermined specifics including a measurable angle of view, a resolution, measurement accuracy and a time period necessary for one measurement. There is a case where the entire surface shape of the measurement object cannot be measured depending on specifics of the three-dimensional measuring device. For example, if a surface shape of the measurement object is complicated or has a narrow hole, there is occurred a dead angle (occlusion) at which the measurement is disabled even if the measurement is performed from any direction. The convenient and current situation is that the three-dimensional measurement is performed as much as possible by the operator's experience and guesswork.
As described above, the current situation is that when a measurement object is measured by a three-dimensional measuring device the measurement ends up depending on the operator's know-how. For this reason, even a skilled operator consumes much time for determining an optimal position relationship for measurement by cut and try and for measuring one point many times by cut-and-try methods. If plural three-dimensional measuring devices are used, each of them may require the measurement of many times by cut-and-try methods. In addition, there is a case where the measurement fails at last after consuming much time for the measurement.
Such a waste of time and efforts may be caused because that it is difficult to determine to which extent the measurement object can be measured by a really available three-dimensional measuring device and that the three-dimensional measurement depends on the operator's know-how.